Renshaw Cells and Muscle Reflexes

by Thad Wilson, PhD

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    00:00 Renshaw Cells Renshaw cells aren’t involved within afferent, efferent reflex.

    00:09 But instead, they are engage when you have a contraction through alpha motor neurons.

    00:15 So this is information being send down the spinal cord to the alpha motor neuron to get a constriction.

    00:22 At the same time as getting the constriction from the alpha motor neuron, there is feedback that is then stimulating the Renshaw cell.

    00:31 That Renshaw cell that gets stimulated then inhibits further alpha motor unit contraction.

    00:38 So this is also is a preventive mechanism, and this is helpful in reducing the amount of force output and limiting the contraction duration.

    00:49 It is spot that this Renshaw cells, might be involve a little bit when a person goes through something like weight training.

    00:57 They start to get stronger, quicker than they are increasing the amount of the muscle mass.

    01:02 So maybe you are releasing some of these inhibition that is put on by a Renshaw cells.

    01:08 Pain Withdraw Reflex This is one of our more complicated reflexes.

    01:14 And involves many aspects including both sides or two limbs.

    01:21 This revolves something like stepping it on something painful.

    01:25 We’ve all done these before. You step on something that was really sharp.

    01:30 There is a reflex that happens that doesn’t involves the brain just the spinal cord for you to respond to these.

    01:36 First, you have this cutaneous pain receptor which is usually a sharp pain being sent up to the spinal cord.

    01:45 That information is sensed at the level of the spinal cord and a reflex response results.

    01:53 The first thing that happens is you have a stimulation to the opposite leg.

    02:00 And that stimulation is to extend the quadriceps and relax the hamstrings.

    02:06 On the leg that is being have the pain stimulus, there is a withdraw reflex.

    02:13 Meaning that you have a reduction in the amount of alpha motor neurons going to the quadriceps and an increase are ones going to the hamstring with your semimembranosus and tendinosis.

    02:27 Why are muscle reflexes so important? The main reason why muscle reflexes are there is to prevent injury.

    02:36 So we saw through things like the stretch reflex.

    02:39 Muscles spindle sensing the amount of stretch and then causing a contraction of that muscle because it was being stretch too much.

    02:48 In Golgi tendon organs, we have a response where there is too much tension on a tendon.

    02:54 Therefore we have to reduce the amount of tension.

    02:57 You do that by relaxing the muscle that is undergoing that increase intension and contracting the opposite muscle group so that you don’t have so much tension on that tendon.

    03:09 With things like the pain reflex, this is a response in which you need to contract some muscles and relax others.

    03:18 And you that all in that effort to prevent yourself from falling.

    03:22 So all these reflexes in combination are there to protect the body from getting injured or falling.

    About the Lecture

    The lecture Renshaw Cells and Muscle Reflexes by Thad Wilson, PhD is from the course Neurophysiology.

    Included Quiz Questions

    1. Alpha motor neurons
    2. Gamma motor neurons
    3. Delta motor neurons
    4. Pain receptors
    5. Temperature receptors
    1. They don’t result in withdrawal from a painful stimulus.
    2. They prevent excessive stretch of the muscle.
    3. They prevent excessive tension on the muscle.
    4. Prevent muscle from tearing.
    5. Prevent injury.

    Author of lecture Renshaw Cells and Muscle Reflexes

     Thad Wilson, PhD

    Thad Wilson, PhD

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